I did douse the lights, but it didn't help much since her lightning bolt attacks were illuminating the area, which let the seven-odd other humans she had around her spot me and clobber me to death. To be honest, it's probably a good thing she was difficult, since the 19-intelligence-and-L3-lightning build I had was letting me blast through most other enemies without issues (provided I could stay human and find food). Hmm... maybe next time I'll try the same build but take Swap as another one of my magic slots and use it to pull her away from her bodyguards into a side-room somewhere before vamping out...
The vamps-ignore-vamps and humans-ignore-humans mechanics don't really make sense and seem a bit artificial and ridiculous when you are murdering their supposed allies right in front of them or switch from one to the other mid-fight (and receive their immediate forgiveness), plus of course there shouldn't really be anything stopping me as the player attacking others of my own kind if I wanted to... but it does lead to some interesting gameplay trying to work around that system, so I'm not too sure what to suggest there.